From 49cb77e297dc611a1b795cfeb79452b3002bd331 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Mon, 27 Mar 2017 16:12:43 -0700 Subject: [PATCH] target: Avoid mappedlun symlink creation during lun shutdown This patch closes a race between se_lun deletion during configfs unlink in target_fabric_port_unlink() -> core_dev_del_lun() -> core_tpg_remove_lun(), when transport_clear_lun_ref() blocks waiting for percpu_ref RCU grace period to finish, but a new NodeACL mappedlun is added before the RCU grace period has completed. This can happen in target_fabric_mappedlun_link() because it only checks for se_lun->lun_se_dev, which is not cleared until after transport_clear_lun_ref() percpu_ref RCU grace period finishes. This bug originally manifested as NULL pointer dereference OOPsen in target_stat_scsi_att_intr_port_show_attr_dev() on v4.1.y code, because it dereferences lun->lun_se_dev without a explicit NULL pointer check. In post v4.1 code with target-core RCU conversion, the code in target_stat_scsi_att_intr_port_show_attr_dev() no longer uses se_lun->lun_se_dev, but the same race still exists. To address the bug, go ahead and set se_lun>lun_shutdown as early as possible in core_tpg_remove_lun(), and ensure new NodeACL mappedlun creation in target_fabric_mappedlun_link() fails during se_lun shutdown. Reported-by: James Shen Cc: James Shen Tested-by: James Shen Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_fabric_configfs.c | 5 +++++ drivers/target/target_core_tpg.c | 4 ++++ include/target/target_core_base.h | 1 + 3 files changed, 10 insertions(+) diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c index d8a16ca6baa5..d1e6cab8e3d3 100644 --- a/drivers/target/target_core_fabric_configfs.c +++ b/drivers/target/target_core_fabric_configfs.c @@ -92,6 +92,11 @@ static int target_fabric_mappedlun_link( pr_err("Source se_lun->lun_se_dev does not exist\n"); return -EINVAL; } + if (lun->lun_shutdown) { + pr_err("Unable to create mappedlun symlink because" + " lun->lun_shutdown=true\n"); + return -EINVAL; + } se_tpg = lun->lun_tpg; nacl_ci = &lun_acl_ci->ci_parent->ci_group->cg_item; diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c index 6fb191914f45..dfaef4d3b2d2 100644 --- a/drivers/target/target_core_tpg.c +++ b/drivers/target/target_core_tpg.c @@ -642,6 +642,8 @@ void core_tpg_remove_lun( */ struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev); + lun->lun_shutdown = true; + core_clear_lun_from_tpg(lun, tpg); /* * Wait for any active I/O references to percpu se_lun->lun_ref to @@ -663,6 +665,8 @@ void core_tpg_remove_lun( } if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE)) hlist_del_rcu(&lun->link); + + lun->lun_shutdown = false; mutex_unlock(&tpg->tpg_lun_mutex); percpu_ref_exit(&lun->lun_ref); diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 4b784b6e21c0..2e282461cfa5 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -705,6 +705,7 @@ struct se_lun { u64 unpacked_lun; #define SE_LUN_LINK_MAGIC 0xffff7771 u32 lun_link_magic; + bool lun_shutdown; bool lun_access_ro; u32 lun_index;